1. Field of the Invention
The present invention relates to a circuit analyzing apparatus, a circuit analyzing method and a circuit analyzing program, and, in particular, to a circuit analyzing apparatus, a circuit analyzing method and a circuit analyzing program for analyzing operating characteristics of a circuit unit having circuit devices arranged on a substrate.
2. Description of the Related Art
Recently, in a circuit unit having circuit devices arranged on a substrate, an influence of parameters (referred to as ‘substrate parameters’, hereinafter) such as a dielectric constant, a dielectric dissipation factor and so forth, having values depending on characteristics of material of the substrate, cannot be ignored in many cases when operating characteristics of the circuit unit are analyzed.
That is, in the analysis for the operating characteristics, respective parameter values on operating frequency/operating temperature, which are conditions for the analysis, are required. In this case, because the substrate parameters such as the above-mentioned dielectric constant (∈r) and the dielectric dissipation factor (tan δ) depend on the operating frequency/temperature, the values according to the corresponding conditions are required. However, in a catalog for the substrate material, the values merely for typical frequency/temperature are given, in many cases.
For example, as shown in FIG. 1, when the analyzing frequency is 2 GHz for example, a designer may use the values given by the catalog as they are even when the catalog values are merely for a different operating frequency of 1 GHz. In such a case, the substrate parameters thus obtained may considerably deviate from the correct values due to the difference in the operating frequency. Therefore, a signal waveform obtained from the analysis may have considerable error accordingly.
Further, in a case where, as shown in FIG. 2, the substrate manufacturer provides two typical values in the catalog, an approximation formula (i.e., a linear function for linear approximation, in many cases) may be used for obtaining the necessary characteristic values from those corresponding to these two values. That is, with the use of the approximation formula, the values on the target analyzing frequency are obtained. However, the calculation by means of the approximation formula of the linear function may inevitably include calculation error in many cases.
Further, in many cases, no information is given from the catalog concerning temperature characteristics of the substrate parameters, and the designer should use the values on the typical temperature given by the catalog in many cases.
No serious issue may arise even when the frequency/temperature characteristics of the substrate parameters are not strictly considered for a case of transmission simulation for a low frequency condition. However, as the operating frequency increases, improvement of the analysis precision is required accordingly, and thus, the necessity of considering the frequency/temperature dependency of the substrate parameters arises.
Japanese Laid-open Patent Applications Nos. 2001-165974, 2005-534083 and 2003-132112 disclose related arts.